Motor - driven vehicle drive control apparatus and method thereof

ABSTRACT

A vehicle drive control apparatus including a motor, a battery, an inverter having a direct current supplied from the battery, wherein the inverter converts the direct current into an alternating current and supplies the alternating current to the motor and a controller that transmits a drive signal to the inverter so as to execute a weak field control, wherein a charging current supplied to the battery, at a time when execution of the weak field control is not allowed, is set to be smaller than an overcharging current indicating a maximum value of an electric current charged in the battery.

BACKGROUND OF THE INVENTION

[0001] 1. Field of Invention

[0002] The invention relates to a motor-driven vehicle drive controlapparatus and method thereof.

[0003] 2. Description of Related Art

[0004] Conventionally, there exists a vehicle driving apparatus that ismounted on an electric car. The vehicle driving apparatus generates amotortorque and transmits the motor torque to a drive wheel. In thisvehicle driving apparatus, a motor is driven by a direct currentapplication from a battery at a time of power running (driving),generates the motor torque, is exposed to a torque caused by an inertiaof the electric car at a time of regeneration (power generation),generates a direct current, and supplies the electric current to thebattery.

[0005] Further, there exists a vehicle driving apparatus that is mountedon a hybrid vehicle that serves as a motor-driven vehicle. The vehicledriving apparatus transmits part of an engine torque to a powergenerator (a power generator motor) corresponding to a firstmotor-driven machine and the rest of the engine torque to a drive wheel.In this vehicle driving apparatus, the vehicle driving apparatus has aplanetary gear unit provided with a sun gear, a ring gear and a carrier.The carrier is connected to the engine, the ring gear is connected tothe drive wheel, the sun gear is connected to the power generator, and arotation output from the ring gear and a motor corresponding to a secondmotor-driven machine is transmitted to the drive wheel, whereby adriving force is generated.

[0006] In the above vehicle driving apparatus, a motor control apparatusis arranged in each vehicle driving apparatus. Both of the motor controlapparatuses are structured such that a feedback control in accordancewith a vector control computation is executed on a d-q axes model inwhich an axis d and an axis q are respectively placed in a direction ofa magnetic pole pair of a rotor in the motor and in a directionperpendicular to the axis d, at a time of supplying the electric currentfrom the battery to the motor and at a time when the motor-drivenvehicle is driven by the motor. Further, when the motor is driven at ahigh speed in the feedback control, an induced voltage becomes high, anda sufficient motor torque can not be generated. Accordingly, when themotor is driven at a high speed, a weak field control is executed byreducing an amount of magnetic flux formed by the d-axis current.

[0007] 2. Summary of the Invention

[0008] However, in the conventional vehicle driving apparatus mentionedabove, when the weak field control can not be executed, for example,when the motor control apparatus can not execute the control because ofa disturbance caused by noise, physical damage and the like, and atleast one of three wires for supplying the electric current to aninverter and to the motor from the inverter is physically broken, a highcounter-electromotive voltage is generated, an excess current issupplied to the battery accompanying therewith, and the battery isovercharged. In general, since a battery having a comparatively highvoltage (for example, 144, 288 or 312 [V]) is used in the electric caror the hybrid vehicle, the electric current supplied to the battery issmall. Therefore, the structure is made such that when the excesscurrent is going to be supplied to the battery, the excess current isprevented from being supplied to the battery by disconnecting a relay ona direct-current cable.

[0009] On the contrary, for example, when the electric car or the hybridvehicle, in which a battery having a comparatively low voltage (forexample, 42 [V]) is employed, the electric current supplied to thebattery is greater by just that much. Accordingly, when it is intendedto disconnect the relay on the direct-current cable when the excesscurrent is going to be supplied to the battery, the relay is on a largescale. Therefore, the vehicle driving apparatus is large-scaled.

[0010] The invention thus provides a motor-driven vehicle drive controlapparatus which can solve the problems in the conventional vehicledriving apparatus mentioned above, can prevent an excess current frombeing supplied to a battery, and can make the apparatus compact.

[0011] In order to achieve the foregoing and other advantages, a vehicledrive control apparatus according to a first exemplary aspect of theinvention includes a motor, a battery, an inverter having a directcurrent supplied from the battery, wherein the inverter converts thedirect current into an alternating current and supplies the alternatingcurrent to the motor and a controller. The controller transmits a drivesignal to the inverter so as to execute a weak field control, wherein acharging current supplied to the battery, at a time when execution ofthe weak field control is not allowed, is set to be smaller than anovercharging current indicating a maximum value of an electric currentcharged in the battery.

[0012] In this case, the charging current supplied to the battery, at atime when the weak field control can not be executed, is made smallerthan the overcharging current expressing the maximum value of theelectric current charged in the battery. Accordingly, even when the weakfield control can not be executed and the high counter-electromotivevoltage is generated, it is possible to prevent the excess current frombeing supplied to the battery, and the battery is not overcharged.Further, since it is not necessary to make the relay on thedirect-current cable large scaled, the vehicle driving apparatus is madecompact.

[0013] A vehicle drive control apparatus according to a second exemplaryaspect of the invention includes a motor with a rotor including aplurality of permanent magnets arranged in a plurality of portions in acircumferential direction and salient poles arranged between thepermanent magnets, a battery, an inverter having a direct currentsupplied from the battery, wherein the inverter converts the directcurrent into an alternating current and supplies the alternating currentto the motor and a controller. The controller transmits a drive signalto the inverter so as to execute a weak field control, wherein areluctance torque coefficient is set to be equal to or more than 40, thereluctance torque coefficient calculated by dividing a torque constant,determined based on the motor torque and the alternating currentsupplied to the motor, by a counter-electromotive constant, thecounter-electromotive constant calculated by dividing a maximumcounter-electromotive voltage generated at a time when execution of theweak field control is not allowed by a maximum value of a motor rotationspeed.

[0014] In this case, since the reluctance torque coefficient is set tobe equal to or more than 40, the use ratio of the reluctance torque ismade higher in the magnet torque generated by the permanent magnet, andthe reluctance torque generated by the salient poles. Accordingly, it ispossible to prevent the battery from being overcharged, and it ispossible to generate a sufficient motor torque.

BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Various embodiments of the invention will be described withreference to the drawings, wherein:

[0016]FIG. 1 is a schematic view of a main portion of a vehicle drivingapparatus according to a first embodiment of the invention;

[0017]FIG. 2 is a block diagram showing a hybrid vehicle drive controlapparatus according to the first embodiment of the invention;

[0018]FIG. 3 is a view of a first example of a rotor according to thefirst embodiment of the invention;

[0019]FIG. 4 is a view of a second example of a rotor according to thefirst embodiment of the invention;

[0020]FIG. 5 is a view of an example of a rotor according to a secondembodiment of the invention; and

[0021]FIG. 6 is a view of a property of a motor according to the secondembodiment of the invention.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

[0022] A description will be given in detail below of embodimentsaccording to the invention with reference to the accompanying drawings.In this case, a description will be given of a vehicle driving apparatusfor driving a hybrid vehicle, provided with an engine, that serves as amotor-driven vehicle. In place of the hybrid vehicle provided with anengine and a motor, the motor-driven vehicle, of the invention can beapplied to a vehicle driving apparatus for driving an electric car whichis not provided with an engine and is provided only with a motor, ahybrid vehicle which is provided with an engine, a power generator and amotor, and the like.

[0023]FIG. 1 is a schematic view of a main portion of a vehicle drivingapparatus according to a first embodiment of the invention. In thedrawing, reference numeral 12 denotes a crank shaft that serves as anoutput shaft directly connected to an engine (not shown), referencenumeral 13 denotes a drive plate, reference numeral 14 denotes a torqueconverter that serves as a fluid transmission gear, reference numeral 25denotes a motor that serves as a motor-driven machinery, and referencenumeral 15 denotes a center piece of the torque converter 14. The torqueconverter 14 is provided with the center piece 15, a front cover 16connected to the center piece 15, a pump impeller 17 connected to thefront cover 16, a turbine runner 21 arranged so as to oppose to the pumpimpeller 17, forming a torus together with the pump impeller 17 andconnected to an input shaft 19 of a gear box via a turbine hub 18, astator 22, a detachably arranged lockup clutch apparatus 23, and adamper apparatus 24 absorbing a fluctuation of a torque transmitted viathe torque converter 14, that is, a transmission torque.

[0024] Further, in the torque converter 14, a rotation transmitted fromthe engine is transmitted to the front cover 16 via the crank shaft 12,and is transmitted to the pump impeller 17 fixed to the front cover 16.In this case, when the pump impeller 17 is rotated, oil within the torusflows around an axis of the torque converter 14, is circulated among thepump impeller 17, the turbine runner 21 and the stator 22 due to acentrifugal force application, rotates the turbine runner 21, and istransmitted to the input shaft 19.

[0025] When a difference in a rotation speed between the pump impeller17 and the turbine runner 21 is large just after the pump impeller 17starts rotating, such as a starting time or the like of the hybridvehicle, the oil flowing out from the turbine runner 21 flows in adirection of preventing the rotation of the pump impeller 17.Accordingly, the stator 22 is arranged between the pump impeller 17 andthe turbine runner 21, and the stator 22 changes the oil flow in adirection of assisting the rotation of the pump impeller 17, at a timewhen the difference of rotation speed between the pump impeller 17 andthe turbine runner 21 is large.

[0026] Further, when the rotation speed of the turbine runner 21 becomeshigh, and the difference in rotation speed between the pump impeller 17and the turbine runner 21 becomes small, the oil brought into contactwith a front side of a blade in the stator 22 is going to be broughtinto contact with a back side thereof, whereby the oil flow isprevented. In order to allow the stator 22 to rotate only in a fixeddirection, a one-way clutch F is arranged in an inner peripheral side ofthe stator 22. Thus, when the oil is going to be brought into contactwith the back side of the blade, the stator 22 is going to be naturallyrotated by the one-way clutch F, so that the oil is smoothly circulated.

[0027] When a preset vehicle speed is obtained after the hybrid vehicleis started, a lockup clutch apparatus 23 is engaged, and the rotation ofthe engine is directly transmitted to the input shaft 19 withoutinvolving oil. In this case, the motor 25 is provided with a stator 28fixed to a vehicle driving apparatus case 26, and a rotor 31 is mountedto the center piece 15 on an inner side in the radial direction ratherthan on the stator 28. The rotor 31 is also rotatably arranged withrespect to the stator 28. The stator 28 is provided with a stator core32, and a coil 33 wound around the stator core 32. The rotor 31 isprovided with a rotor core 34 and a plurality of permanent magnets 35arranged in a plurality of portions in a circumferential direction ofthe rotor core 34. The rotor 31 is centered to the center piece 15 via arotor hub 36, and the rotor hub 36 is connected to the front cover 16and is connected to the drive plate 13 via an annular plate 38. In thiscase, reference symbols bt1 and bt2 denote a bolt.

[0028] Next, a description will be given of the hybrid vehicle drivecontrol apparatus corresponding to the motor-driven vehicle drivecontrol apparatus. FIG. 2 is a block diagram showing a hybrid vehicledrive control apparatus according to the first embodiment of theinvention.

[0029] In the drawing, reference numeral 11 denotes an engine, referencenumeral 12 denotes a crank shaft, reference numeral 14 denotes a torqueconverter, reference numeral 25 denotes a motor, reference numeral 29denotes an inverter that serves as a motor inverter for driving themotor 25, reference numeral 37 denotes a drive wheel, reference numeral41 denotes a gear box connected to the torque converter 14 and changingthe rotation output from the torque converter 14 according to apredetermined transmission speed range, reference numeral 43 denotes amain battery that serves as a first battery forming a power source formaking the hybrid vehicle travel, and reference numeral 45 denotes anauxiliary battery that serves as a second battery forming a power sourcefor operating auxiliary machines of the hybrid vehicle. The inverter 29is connected to the main battery 43 via a main relay 47 that serves as arelay and direct current cables CB1 and CB2, and a direct current issupplied to the inverter 29 from the main battery 43. Further, the mainbattery 43 is connected to a DC/DC converter 48 via the main relay 47,the direct current cables CB1 and CB2, and direct current cables CB3 andCB4 branched from the direct current cables CB1 and CB2, and the DC/DCconverter 48 and the auxiliary battery 45 are connected.

[0030] In the present embodiment, an electric voltage corresponding to afirst power source voltage in the main battery 43 is 42 [V], an electricvoltage corresponding to a second power source voltage in the auxiliarybattery 45 is 12 [V], and the DC/DC converter 48 converts the electricvoltage of 42 [V] into the electric voltage of 12 [V] or converts theelectric voltage of 12 [V] into the electric voltage of 42 [V]. Further,a switch 56 is arranged within the DC/DC converter 48. It is possible tooperate the DC/DC converter 48 or stop the operation of the DC/DCconverter 48 by turning on or off the switch 56.

[0031] A motor inverter voltage sensor 76 that serves as a directcurrent voltage detecting portion is arranged in an inlet side of theinverter 29 for detecting a direct current voltage applied to theinverter 29, that is, a motor inverter voltage VM. A motor invertercurrent sensor 78 corresponding to a direct current detecting portion isarranged in a predetermined portion of the direct current cable CB2 fordetecting a direct current supplied to the inverter 29, that is, a motorinverter current IM. Further, the motor inverter voltage VM is fed to avehicle control apparatus 51, and the motor inverter current IM is fedto a motor control apparatus 49. In this case, a smoothing condenser Cis connected between the main battery 43 and the inverter 29.

[0032] Further, the vehicle control apparatus 51 comprises a CPU, arecording apparatus and the like which are not illustrated, executes anentire control of the vehicle driving apparatus, and functions as acomputer on the basis of a predetermined program, data and the like. Thevehicle control apparatus 51 is connected to the engine controlapparatus 46, the motor control apparatus 49 and an automatictransmission control apparatus 52. Further, the engine control apparatus46 comprises a CPU, a recording apparatus and the like which are notillustrated, and transmits an instruction signal such as a throttleopening degree θ, a valve timing and the like, for controlling theengine 11. Further, the motor control apparatus 49 comprises a CPU, arecording apparatus and the like which are not illustrated, andtransmits a drive signal to the inverter 29 for controlling the motor25. Further, the automatic transmission control apparatus 52 comprises aCPU, a recording apparatus and the like which are not illustrated, andtransmits respective signals such as a solenoid signal and the like tothe gear box 41 for controlling the automatic transmission. In thiscase, a first control apparatus comprises the engine control apparatus46, the motor control apparatus 49 and the automatic transmissioncontrol apparatus 52, and a second control apparatus existing in asuperior position of the first control position comprises the vehiclecontrol apparatus 51. Further, the engine control apparatus 46, themotor control apparatus 49 and the automatic transmission controlapparatus 52 function as a computer on the basis of a predeterminedprogram, data and the like, in the same manner as that of the vehiclecontrol apparatus 51.

[0033] The inverter 29 is driven in accordance with the drive signal, isexposed to the direct current from the main battery 43 at a time ofpower running, generates respective phases of currents IMU, IMV and IMW,supplies the respective phase of currents IMU, IMV and IMW to the motor25, receives the respective phase of currents IMU, IMV and IMW from themotor 25 at a time of regeneration, generates a direct current andsupplies the direct current to the main battery 43.

[0034] Further, reference numeral 44 denotes a battery state-of-chargedetecting apparatus for detecting a state of the main battery 43, thatis, a battery state-of-charge SOC corresponding to a battery state,reference numeral 53 denotes a shift position sensor for detecting aposition of a shift lever (not shown) that serves as a shift operatingportion, that is, a shift position SP, reference numeral 55 denotes anaccelerator switch that serves as a engine load detecting portion and anaccelerator operation detecting portion for detecting a position (adepressed amount) of an accelerator pedal (not shown), that is, anaccelerator pedal position AP, reference numeral 62 denotes a brakeswitch that serves as a brake operation detecting portion for detectinga position (a depressed amount) of a brake pedal (not shown), that is, abrake pedal position BP, and reference numeral 63 denotes a batterytemperature sensor that serves as a temperature detecting portion fordetecting a temperature tmB of the main battery 43. In this case, a loadapplied to the engine 11, that is, an engine load is expressed by theaccelerator pedal position AP.

[0035] Further, reference numerals 68 and 69 denote an electric currentsensor that serves as an alternating current detecting portion and atemperature detecting portion for detecting the respective phase ofcurrents IMU and IMV, and reference numeral 72 denotes a battery voltagesensor corresponding to a voltage detecting portion for the main battery43 for detecting the battery voltage VB corresponding to the batterystate. The battery voltage VB is fed to the vehicle control apparatus51. Further, it is possible to detect a battery current, a batterytemperature and the like as the battery state. In this case, a batterystate detecting portion comprises the battery state-of-charge detectingapparatus 44, the battery voltage sensor 72 and the battery currentsensor (not shown), the battery temperature sensor (not shown) and thelike. Further, the currents IMU and IMV are supplied to the motorcontrol apparatus 49 and the vehicle control apparatus 51.

[0036] The vehicle control apparatus 51 transmits the engine controlsignal to the engine control apparatus 46, and makes the engine controlapparatus 46 set the drive and stop of the engine 11. Further, vehiclespeed calculating processing means (not shown) of the vehicle controlapparatus 51 executes vehicle speed calculating processing, reads aposition of the rotor 31 (FIG. 1) of the motor 25, that is, a rotorposition, calculates a change rate of the rotor position, and calculatesa vehicle speed on the basis of the change rate, and a gear ratio in atorque transmission system from the center piece 15 to the drive wheel37.

[0037] Further, the vehicle control apparatus 51 sets an engine targetrotation speed NE* expressing a target value of the engine rotationspeed NE, and a motor target torque TM* expressing a target value of themotor torque TM. In the present embodiment, the structure is made suchthat the motor 25 is used as a starter for starting the engine 11, andis also used as a power generator. However, the structure may be madesuch that the motor 25 is used as an auxiliary drive source at a timewhen the engine torque TE is changed due to a change in the throttleopening degree θ of the engine 11.

[0038] Next, a description will be given of an operation of the motorcontrol apparatus 49. In this case, the motor control apparatus 49executes a feedback control in accordance with a vector controlcomputation on a d-q axes model in which an axis d and an axis q arerespectively placed in a direction of a magnetic pole pair of the rotor31 in the motor 25 and in a direction perpendicular to the axis d.

[0039] First, motor rotation speed calculating processing means (notshown) of the motor control apparatus 49 executes motor rotation speedcalculating processing, reads the rotor position and calculates a changerate of the rotor position, thereby calculating the rotation speed ofthe motor 25, that is, a motor rotation speed NM.

[0040] Subsequently, motor control processing means (not shown) of themotor control apparatus 49 executes motor control processing, reads themotor target torque TM* and the battery voltage VB, makes reference to acurrent instruction value map for controlling the motor recorded in therecording apparatus of the motor control apparatus 49 on the basis ofthe motor rotation speed NM, the motor target torque TM* and the batteryvoltage VB, and calculates and determines a d-axis current instructionvalue IMd* and a q-axis current instruction value IMq*.

[0041] Further, the motor control processing means reads the electriccurrents IMU and IMV from the current sensors 68 and 69, and calculatesthe electric current IMW on the basis of the electric currents IMU andIMV in accordance with the formula IMW=IMU−IMV. In this case, theelectric current IMW may be detected by the current sensor in the samemanner as the electric currents IMU and IMV.

[0042] Subsequently, alternating current calculating processing means(not shown) of the motor control processing means executes alternatingcurrent calculating processing, and calculates a d-axis current IMd anda q-axis current IMq corresponding to the alternating current. For thispurpose, the alternating current calculating processing means executes athree-phase/two-phase conversion so as to convert the electric currentsIMU, IMV and IMW into the d-axis current IMd and the q-axis current IMq.Further, alternating voltage instruction value calculating processingmeans (not shown) of the motor control processing means executesalternating voltage instruction calculating processing, and calculatesvoltage instruction values VMd* and VMq* on the basis of the d-axiscurrent IMd, the q-axis current IMq, the d-axis current instructionvalue IMd* and the q-axis current instruction value IMq*. Further, themotor control processing means executes a two-phase/three-phaseconversion so as to convert the voltage instruction values VMd* and VMq*into the voltage instruction values VMU*, VMV* and VMW*, calculatespulse width modulation signals SU, SV and SW on the basis of the voltageinstruction values VMU*, VMV* and VMW*, and outputs the pulse widthmodulation signals SU, SV and SW to drive processing means (not shown)of the motor control apparatus 49. The drive processing means executesdrive processing, and transmits a drive signal to the inverter 29 on thebasis of the pulse width modulation signals SU, SV and SW. The feedbackcontrol is executed in the manner mentioned above.

[0043] In this case, when this kind of motor 25 is driven at a highspeed, an induced voltage becomes high, and a sufficient motor torque TMcan not be generated. Accordingly, a weak field control means (notshown) of the motor control apparatus 49 executes weak field controlprocessing so as to make the d-axis current instruction value IMd* smallat a time when the motor 25 is driven at a high speed, for example, at atime when the motor rotation speed NM is a threshold value, therebyexecuting the weak field control by reducing an amount of magnetic fluxin a magnetic field formed by the d-axis current IMd.

[0044] However, if the weak field control can not be executed for somereason, for example, because the motor control apparatus 49 can notexecute the control due to a disturbance caused by a noise, a physicaldamage or the like, or the inverter 29 and at least one of three wiresfor supplying the electric currents IMU, IMV and IMW to the motor 25from the inverter 29, a high counter-electromotive voltage E0 isgenerated. Further, if the excess current is supplied to the mainbattery 43 accompanying therewith, the main battery 43 is excessivelycharged. Since the main battery having a comparatively (for example,144, 288 and 312 [V]) is generally used in the electric car or thehybrid vehicle, the electric current supplied to the main battery issmall. Accordingly, if the excess current is going to be supplied to themain battery, a relay on the direct-current cable is disconnected,whereby it is possible to prevent the excess current from being suppliedto the battery.

[0045] On the contrary, in the case of the electric car or the hybridvehicle employing the main battery 43 having a comparatively low voltage(for example, 42 [V]), as in the present embodiment, the electriccurrent supplied to the main battery 43 is larger by just that much.Accordingly, when the main relay 47 is intentionally disconnected on thedirect-current cables CB1 and CB2 at a time when the excess current isgoing to be supplied to the main battery 43, the main relay 47 becomeslarge scaled. Therefore, not only the vehicle driving apparatus is largescaled, but also a micro arcing phenomenon is generated, so that a longtime is required until the main relay 47 is disconnected.

[0046] As a result, the excess current is supplied to the main battery43, and the main battery 43 is excessively charged. Further, forexample, when a nickel hydride battery is used as the main battery 43,generation amounts of hydrogen gas and oxygen gas are increased due toan overcharge of the main battery 43.

[0047] Specifically, reactions shown by the following formulas aregenerated in a nickel positive electrode and an MH negative electrode ofthe nickel hydride battery.

Ni(OH)₂+OH⁻->NiOOH+H₂O+e⁻

M+xH₂O+xe⁻->MHx+xOH⁻

[0048] As a matter of fact, a water generation is not sufficient in thenickel positive electrode at an end stage of the charging, at theexcessively charging time or the like, whereby the oxygen gas isgenerated. Further, an occlusion in a hydrogen absorbing alloy is notsufficient in the MH negative electrode, so that the hydrogen gas isgenerated.

[0049] For example, in the case that in the electric current 300 [A]supplied to the main battery 43, the electric current 200 [A] is usedfor charging, and the rest of the electric current 100 [A] is used forgenerating the oxygen gas and the hydrogen gas, a gas amount of theoxygen gas and the hydrogen gas generated per second can be calculatedby the following formula. Specifically, a quantity of electricity Q ofthe electric current 100 [A] is obtained by the following formula.$\begin{matrix}{Q = {{100\lbrack A\rbrack} \times {1\lbrack s\rbrack}}} \\{= {100\lbrack C\rbrack}} \\{= {100/{96490\lbrack F\rbrack}}} \\{= {10.36 \times {10^{- 4}\lbrack F\rbrack}}}\end{matrix}$

[0050] In this case, when 0.5 [mol] of the hydrogen gas is generated and0.25 [mol] per 1 [F] of the oxygen gas is generated, the followingamount of substance of the hydrogen gas is generated.

10.36×10⁴/2=5.18×10⁻⁴ [mol] in 10.36×10⁻⁴ [F]

[0051] The following amount of the oxygen gas is generated.

10.36×10⁻⁴/4=2.59×10⁻⁴ [mol] in 10.36×10⁻⁴ [F]

[0052] Further, a volume of the hydrogen gas is as follows.

22400 [ml]×5.18×10⁻⁴=11.603 [ml]

[0053] A volume of the oxygen gas is as follows.

22400 [ml]×2.59×10⁻⁴=5.802 [ml]

[0054] Further, even during a period when a normal charging is executed,the hydrogen gas and the oxygen gas are slightly generated. Therefore,the water is generated by immediately recombining the hydrogen gas andthe oxygen gas generated at a time of designing the main battery 43. Inthis case, an exposed nickel surface of the nickel hydride batteryconstitutes a catalyst, thereby promoting recombination of the hydrogengas and the oxygen gas.

[0055] In this case, if the hydrogen gas and the oxygen gas are storedtoo much within the main battery 43, the hydrogen gas and the oxygen gasare rapidly recombined, undesirably.

[0056] Assumingly, an overcharging current IBmax [A] expressing amaximum value of the electric current charged in the main battery 43 anddefined as a rated current for each kind of the main battery 43 is setto a limit value corresponding to the main battery 43, and a currentthat is supplied to the main battery 43 at a time when the weak fieldcontrol can not be executed is set as a charging current Ib [A]. In thiscase, the vehicle driving apparatus is designed and an equipmentconstant of the vehicle driving apparatus is set so that the relation inthe following formula (1) is established.

Ib<IBmax  (1)

[0057] Assumingly, a current when the hydrogen gas and the oxygen gasare stored too much within the main battery 43 and the hydrogen gas andthe oxygen gas are rapidly recombined is a limit current IBLT [A], theovercharging current IBmax defined as a rated current in the presentembodiment can be calculated by multiplying a limit current IBLT [A]with a safety factor ρ in accordance with the following formula.

IBmax=ρ·IBLT

[0058] Moreover, the overcharging current IBmax [A] can also becalculated by further multiplying an adjustment value η takingdurability and the like of the main battery 43 into consideration inaccordance with the following formula.

IBmax=η·ρ·IBLT

[0059] Note that when the overcharging current IBmax is not defined as arated current, it can be calculated in accordance with each formula asmentioned above.

[0060] Therefore, there is provided a first method of setting anequipment constant of the vehicle driving apparatus so that theaforementioned formula (1) is established. In the first method, aninductance Lm [mH] of the coil 33 corresponding to a resistancecomponent R [Ω] of the vehicle driving apparatus, and a conductorresistance between the terminals of the main battery 43 comprises theresistances such as the coil 33, the direct-current cables CB 1 and CB2and the like, that is, a conductor resistance between terminals Rm [m Q]are reduced.

[0061] Further, there is provided a second method in which acounter-electromotive voltage constant Ke [mV/rpm]=Emax/NMmax expressedby dividing a maximum counter-electromotive voltage E0 generated at atime when the weak field control can not be executed, that is, a maximumcounter-electromotive voltage Emax [V] by a maximum value NMmax of themotor rotation speed NM is reduced, or the maximum value NMmax isreduced. In this case, since the engine 11 and the motor 25 are directlyconnected, the maximum value NMmax equals a maximum value NEmax of theengine rotation speed NE.

[0062] Further, in order to enlarge an output of the motor 25corresponding to a property of the motor 25, and the motor torque TM, itis necessary to make the inductance Lm [mH] small or make the conductorresistance between terminals Rm [mΩ] small. Also, it is preferable toincrease the magnetic flux amount of the permanent magnet so as to makethe counter-electromotive voltage E0 high. However, taking protection ofthe main battery 43 into consideration, it is desirable to employ thefirst and second methods.

[0063] In this case, the charging current Ib can be calculated in thefollowing manner. Specifically, on the assumption that a number of amagnetic pole of the motor 25 is set to P, an impedance mainly of thecoil 33 is set to Z, an electric voltage of the main battery 43 itselfafter taking out the wire connection is set to VBdc [V], an alternatingcurrent conversion value of the electric voltage VBdc is set to VBac,and an internal resistance of the main battery 43 is set to Rb [m Ω], aresistance component R of the vehicle driving apparatus is expressed bythe following formula.

R=(π²/18)·Rb+Rm

[0064] The alternating current conversion value VBac is expressed by thefollowing formula.

VBac=(π/3)·VBdc·VB/{square root}  (6)

[0065] Further, a maximum angular velocity co of the motor 25 isexpressed by the following formula.

ω=2π·(NMmax/60)·(P/2)

[0066] Further, the impedance Z is expressed by the following formula.

Z={square root}(R ²+(ω·Lm)²)

[0067] An alternating current Im [A] generated in the coil 33 at a timewhen the weak field control can not be executed is expressed by thefollowing formula.

Im=(−VBac·R+{square root}(VBac ² ·R ² −·Z ²·(VBac ² −Emax ²))/Z ²

[0068] The charging current Ib is expressed by the following formula.

Ib=Im·p/{square root}  (6)

[0069] As mentioned above, it is possible to make the charging currentIb [A] smaller than the overcharging current IBmax by enlarging theresistance component R [Ω] of the vehicle driving apparatus or makingthe counter-electromotive voltage constant Ke [mV/rpm] or the maximumvalue NMmax small. Therefore, it is possible to prevent the excesscurrent from being supplied to the main battery 43 even when the weakfield control can not be executed due to some kind of reason and thehigh counter-electromotive voltage E0 is generated, so that the mainbattery 43 is not overcharged. Further, it is not necessary to make themain relay 47 on the direct-current cables CB1 and CB2 large scaled,thereby making the vehicle driving apparatus compact.

[0070] Meanwhile, in the present embodiment, the structure is made suchthat the permanent magnets are arranged in a plurality of positions inthe circumferential direction of the rotor 31, the salient polesintegrally formed with the rotor core 34 are formed between thepermanent magnets in the circumferential direction. The motor torque TMis generated by utilizing the combination of the magnet torque generatedby the permanent magnet and the reluctance torque generated by thesalient poles.

[0071] In this kind of motor 25, the structure is made such that a useratio of each of the magnet torque and the reluctance torque is set. Theuse ratio of the reluctance torque is made higher, for the purpose ofpreventing the main battery 43 from being overcharged and generating asufficient motor torque TM.

[0072] Accordingly, on the assumption that the torque constant is set toTc [Nm/A·rms], a preset threshold value of a reluctance torquecoefficient α expressing the use ratio α=Tc/Ke is set to be equal to ormore than 40 in the present embodiment. In this case, the torqueconstant Tc can be calculated as follows. Specifically, on theassumption that an effective magnetic flux of a gap per one pole in thepermanent magnets is set to φ [Wb], the effective magnetic flux φg isexpressed by the following formula.

φg=120·Ke/(2.22·P·W·Kw)

[0073] In this case, reference symbol W denotes a number of serialelectric conductors in the motor 25, and reference symbol Kw denotes awinding factor of the coil 33.

[0074] Further, a flux linkage φ [Wb] by the permanent magnets isexpressed by the following formula.

f=P·t·fg·Kw{square root}(3/2)

[0075] In this case, reference symbol t denotes a winding number of thecoil 33.

[0076] In this case, the electric current Im can be expressed by thed-axis current IMd and the q-axis current IMq, and the following formulais established.

Im=(IMd ² +IMq ²)/{square root}(3)

[0077] Further, assumingly, an armature self inductance of the axis dobtained by converting the inductance Lm into a value on the d-q axismodel is set to Ld [H], and an armature self inductance of the axis q isset to Lq [H], there is established the following torque-currentrelation formula which expresses a relation between the motor torque TM,and the d-axis current IMd and the q-axis current IMq.

TM=(P/2)·φ·IMq+(P/2)·(Lq−Ld)·(−Ld)·IMq

[0078] Further, the torque constant Tc is expressed by the followingformula.

Tc=({square root}(3)·TM)/{square root}(IMd ² +IMq ²)

[0079] Accordingly, the reluctance torque coefficient α is expressed bythe following formula (2).

α=Tc/Ke

=({square root}(3)·T)/({square root}(IMd ² +IMq ²)·Ke)  (2)

[0080] As mentioned above, it is preferable to set thecounter-electromotive voltage constant Ke, the inductance Lm, theconductor resistance between terminals Rm and the maximum value NMmax insuch a manner that the formula (1) mentioned above is satisfied and thereluctance torque coefficient α becomes equal to or more than 40.

[0081] Note that the actual charging current Ib[A] can be measured by acurrent sensor arranged in the inverter 29, or it can be measured by acurrent sensor arranged on the direct-current cables CB1 and CB2 thatconnect the inverter 29 and the main battery 43 when the motor 25 isdriven at the maximum value NMmax of the motor rotation speed NM.Further, as mentioned above, since the engine 11 and the motor 25 aredirectly connected in the present embodiment, and thus the maximum valueNMmax equals the maximum value NEmax. Therefore, it is possible to set acurrent measured by each current sensor when the engine 11 is rotated atthe maximum value NEmax at which a lev limiter functions to be thecharging current IB[A]. Note that when the engine 11 and the motor 25are not directly connected, the maximum value NMmax is set to be themaximum motor rotation speed NE of the motor 25 on design.

[0082] Further, the actual maximum electrocounter voltage Emax [V] iscalculated in the following manner. First, after the inverter 29 and themotor 25 are disconnected, the maximum voltage between two phasecurrents out of the each of the respective currents IMU, IMV, and IMW ismeasured, and the maximum voltage is divided by {square root}(3) so asto obtain the maximum voltage value corresponding to one phase. Next,the maximum voltage value corresponding to one phase is divided by{square root}(2) to obtain the effective value thereof. The actualmaximum electrocounter voltage Emax [V] is calculated as the effectivevalue.

[0083] Further, the actual torque constant Tc is calculated in thefollowing manner. First, the currents IMU, IMV, and IMW are detectedwhen the motor torque TM becomes the maximum, and the effective value iscalculated based on the currents IMU, IMV, and IMW. Finally, the maximummotor torque TM is devided by the effective value to obtain the actualtorque constant Tc.

[0084] Next, a description will be given of a structure of the motor 25.FIG. 3 is a view of a first example of a rotor according to the firstembodiment of the invention. FIG. 4 is a view of a second example of arotor according to the first embodiment of the invention.

[0085] In the drawings, reference numeral 28 denotes a stator, referencenumeral 31 denotes a rotor, reference numeral 32 denotes a stator core,and reference numeral 34 denotes a rotor core. The rotor 31 is providedwith the permanent magnets 39 arranged in a plurality of positions, intwelve positions in the present embodiment in a circumferentialdirection by a uniform pitch, and the salient poles 57 arranged in thecenter between the permanent magnets 39 by a uniform pitch, and grooves58 and 59 are formed between the permanent magnets 39 and the salientpoles 57. Further, a holding portion 65 that serves as a magnet portionis formed integrally with the rotor core 34 so as to surround thepermanent magnet 39. The holding portion 65 holds the permanent magnet39 against a centrifugal force at a time when the rotor 31 is rotated.Further, seventy two teeth 61 are formed in the stator core 32 so as toprotrude toward an inner side in a radial direction by a uniform pitch,and a slot 64 is formed between the teeth portions 61.

[0086] In this case, on the assumption that an opening angle of thesalient pole 57 in the circumferential direction of the rotor 31 is setto θp, it is necessary to maximize the reluctance torque generated inaccordance with the driving of the motor 25 (FIG. 2) and to control thecogging torque generated in accordance with the driving of the motor 25in order to minimize the vibration. Therefore, the opening angle θp isset to about a 45 [°] electrical angle. In this case, in the presentembodiment, seventy two slots 64 are formed in the stator core 32, andsix slots 64 are formed per one pole. In this case, the opening angle Opof 45 [°] corresponds to 1.5 slots 64, i.e., has a slot pitch of 1.5.

[0087] Further, on the assumption that the opening angle of the holdingportion 65 in the circumferential direction of the rotor 31 is set toθm, it is necessary to prevent the main battery 43 from beingovercharged and to minimize the cogging. Therefore, the opening angle θmis set to about a 15, 45 or 75 [°] electrical angle. In this case, theopening angle θm of 15, 45 or 75 [°] mentioned above corresponds to 0.5,1.5 or 2.5 slots 64, i.e., as a slot pitch of 0.5, 1.5 or 2.5. FIG. 3shows the example of the rotor 31 in which the opening angle θm is setto 75 [°], and FIG. 4 shows the example of the rotor 31 in which theopening angle θm is set to 45 [°].

[0088] When using the rotor provided with no holding portion 65, thepermanent magnet itself forms the magnet portion, and the opening angleof the permanent magnet in the circumferential direction of the rotor(in FIG. 3 and FIG. 4, the rotor 31 is provided with the holding portion65, however, if the rotor is not provided with the holding portion 65,an angle formed between a line connecting a point A and a point O and aline connecting a point B and the point O) is set to θm.

[0089] In this case, the permanent magnet 39 has a strip shape, is duginto an iron core of the rotor core 34, and is held by the holdingportion 65 in the manner mentioned above. The holding portion 65comprises a bridge portion 66 extending along the circumferentialdirection of the rotor 31 in an outer side of each of the permanentmagnet 39 in the radial direction, and a connection portion 67 extendingin the radial direction along a side wall of the permanent magnet 39.Further, the connection portion 67 has a narrow beam shape extending bya uniform thickness in order to minimize a leakage of the magnetic fluxvia the connection portion 67. In this case, since only a tensile forceis applied to the connection portion 67, it is possible to set theconnection portion 67 comparatively narrow.

[0090] Next, a description will be given of a second embodimentaccording to the invention. In this case, the same reference numeralsare attached to the same elements as those of the first embodiment and adescription thereof will be omitted.

[0091]FIG. 5 is a view of an example of a rotor according to the secondembodiment of the invention, and FIG. 6 is a view of a property of amotor according to the second embodiment of the invention. In this case,in the drawing, a magnetic field angle is set to a horizontal axisexpressing the current phase, and a torque is set to a vertical axis.

[0092] In the drawing, reference numeral 28 denotes a stator, referencenumeral 31 denotes a rotor, reference numeral 32 denotes a stator core,and reference numeral 34 denotes a rotor core. The rotor 31 is providedwith the permanent magnets 39 arranged in a plurality of positions, intwelve positions in the present embodiment in a circumferentialdirection by a uniform pitch, and the salient poles 57 arrangeddownstream from the center between the individual permanent magnets 39by a uniform pitch in a rotation direction (a clockwise direction inFIG. 5) of the motor 25. A groove 73 is formed between the salient pole57 and the permanent magnet 39 in an upstream side in the rotationdirection, and a groove 74 is formed between the salient pole 57 and thepermanent magnet 39 in a downstream side in the rotation direction. Inthis case, an electrical angle is larger in the groove 73 than in thegroove 74. Further, a holding portion 65 that serves as a magnet portionis formed integrally with the rotor core 34 so as to surround thepermanent magnet 39. The holding portion 65 holds the permanent magnet39 against a centrifugal force at a time when the rotor 31 is rotated.Further, seventy two teeth 61 are formed in the stator core 32 so as tobe protruded toward an inner side in a radial direction by a uniformpitch, and a slot 64 is formed between the teeth portions 61.

[0093] Further, it is necessary to minimize the reluctance torquegenerated in accordance with the driving of the motor 25 and to controlthe cogging torque generated in accordance with the driving of the motor25 in order to minimize the vibration. Therefore, the opening angle θpis set to about 45 [°]. In this case, in the present embodiment, seventytwo slots 64 are formed in the stator core 32, and six slots 64 areformed per one pole. In this case, the opening angle Op of 45 [°]corresponds to 1.5 slots 64.

[0094] Further, it is necessary to prevent the main battery 43 frombeing overcharged and to minimize the cogging torque. Therefore, theopening angle θm is set to about 15, 45 or 75 [°]. In this case, theopening angle θm of 15, 45 or 75 [°] mentioned above corresponds to 0.5,1.5 or 2.5 slots 64. FIG. 5 shows the example of the rotor 31 in whichthe opening angle θm is set to 75 [°].

[0095] In this case, in accordance with the present embodiment, sincethe motor 25 is connected to the crank shaft 12, the motor 25 is rotatedonly in a forward direction, that is, in a clockwise direction in FIG. 5in accordance with the driving of the engine 11 in a forward direction.

[0096] In this case, at a time of driving the motor 25, it is possibleto express a position of an electromagnet formed by each of the coils 33of the stator 28, that is, a position indicating a center of themagnetic field in a side of the stator 28 by the magnetic field angle,and the magnetic field angle is set to 0 [°] in a center positionbetween the permanent magnets 39 in the circumferential direction, and acenter position of each of the salient poles 57 in the circumferentialdirection.

[0097] Further, as shown by a line L1 in FIG. 6, the magnet torquegenerated by the permanent magnet 39 becomes maximum at the magneticfield angle of 0 [°]. Further, as shown by a line L2 in FIG. 6, thereluctance torque generated by the salient pole 57 becomes larger as themagnetic field angle is larger than 0 [°]. Accordingly, an added torqueobtained by adding the magnetic torque to the reluctance torque becomesas shown by a line L3 in FIG. 6. As a result, it is possible to generatethe motor torque TM expressed by the added torque.

[0098] Further, as shown in the first embodiment mentioned above, whenthe salient pole 57 is arranged in the center between the permanentmagnets 39, the magnet torque and the reluctance torque, on theassumption that the magnetic field angle at a time of power running ofthe motor 25 is set to 30 [°], both employ values at the magnetic fieldangle of 30 [°] When displacing the salient pole 57 from the centerbetween the permanent magnets 39 to a downstream side by the electricalangle of 15 [°], that is, 0.5 slots 64, in the case that the magneticfield angle at a time of power running of the motor 25 is set to 25 [°],the magnet torque employs a value at a time when the magnetic fieldangle is 25 [°], and the reluctance torque employs a value at a timewhen the magnetic field angle is 40 [°] which is obtained by adding 15[°] to 25 [°]. Accordingly, since both of the magnet torque and thereluctance torque become large values, the added torque is furtherenlarged.

[0099] In this case, when regenerating the motor 25, the rotor 31outputs the motor torque TM in the reverse direction. Accordingly, apolarity of the electromagnet of the stator 28 is set in reverse byadding the magnetic field angle of 180 [°] to the magnetic field angleat a time of power running. In this case, the motor torque TM becomessmall, however, no problem is generated at a time of regenerating evenin the case that the motor torque TM is small.

[0100] In this case, the invention is not limited to the embodimentsmentioned above, and can be variously modified on the basis of the scopeof the invention. These modifications are not excluded from the scope ofthe invention.

1. A motor-driven vehicle drive control apparatus comprising: a motor; abattery; an inverter having a direct current supplied from said battery,converting said direct current into an alternating current and supplyingthe alternating current to said motor; and weak field control processingmeans for transmitting a drive signal to said inverter so as to executea weak field control, characterized in that a charging current suppliedto said battery at a time when the weak field control is not allowed tobe executed is set to be smaller than an overcharging current indicatinga maximum value of an electric current charged in said battery.
 2. Themotor-driven vehicle drive control apparatus according to claim 1,wherein the charging current is supplied to the battery when the motoris driven at a maximum motor rotation speed.
 3. The motor-driven vehicledrive control apparatus according to claim 1, wherein an electricresistive component of the vehicle driving apparatus is set such thatsaid charging current is made smaller than the overcharging current. 4.The motor-driven vehicle drive control apparatus according to claim 1,wherein a counter-electromotive voltage constant expressed by dividing amaximum counter-electromotive voltage generated at a time when the weakfield control is not allowed to be executed by a maximum value of amotor rotation speed is set, such that said charging current becomessmaller than the overcharging current.
 5. The motor-driven vehicle drivecontrol apparatus according to claim 3, wherein a counter-electromotivevoltage constant expressed by dividing a maximum counter-electromotivevoltage generated at a time when the weak field control is not allowedto be executed by a maximum value of a motor rotation speed is set, suchthat said charging current becomes smaller than the overchargingcurrent.
 6. The motor-driven vehicle drive control apparatus accordingto claim 1, wherein a maximum value of a motor rotation speed is setsuch that said charging current becomes smaller than the overchargingcurrent.
 7. A motor-driven vehicle drive control apparatus comprising: amotor; a battery; an inverter having a direct current supplied from saidbattery, converting said direct current into an alternating current andsupplying the alternating current to said motor; and weak field controlprocessing means for transmitting a drive signal to said inverter so asto execute a weak field control, wherein a rotor of said motor includinga plurality of permanent magnets arranged in a plurality of portions ina circumferential direction, and salient poles arranged between saidpermanent magnets, characterized in that on the assumption that a torqueconstant determined on the basis of the motor torque and the alternatingcurrent supplied to said motor is set to Tc, and a counter-electromotiveconstant expressed by dividing a maximum counter-electromotive voltagegenerated at a time when the weak field control is not allowed to beexecuted by a maximum value of a motor rotation speed is set to Ke, areluctance torque coefficient α=Tc/Ke is set to be equal to or more than40.
 8. The motor-driven vehicle drive control apparatus according toclaim 1, wherein a rotor of said motor is further provided with aplurality of permanent magnets arranged in a plurality of portions in acircumferential direction, and salient poles arranged between saidpermanent magnets, and wherein an opening angle of the salient poles isset so as to correspond to 1.5 slots, and an opening angle of thepermanent magnets is set so as to correspond to 0.5, 1.5 or 2.5 slots.9. The motor-driven vehicle drive control apparatus according to claim7, wherein a rotor of said motor is further provided with a plurality ofpermanent magnets arranged in a plurality of portions in acircumferential direction, and salient poles arranged between saidpermanent magnets, and wherein an opening angle of the salient poles isset so as to correspond to 1.5 slots, and an opening angle of thepermanent magnets is set so as to correspond to 0.5, 1.5 or 2.5 slots.10. The motor-driven vehicle drive control apparatus according to claim1, wherein a rotor of said motor is further provided with a plurality ofpermanent magnets arranged in a plurality of portions in acircumferential direction, and salient poles arranged between saidpermanent magnets, and wherein in a holding portion holding saidpermanent magnets, a connection portion extending in a radial directionalong side walls of the permanent magnets has a shape of a narrow beamextending in a uniform thickness.
 11. The motor-driven vehicle drivecontrol apparatus according to claim 7, wherein a rotor of said motor isfurther provided with a plurality of permanent magnets arranged in aplurality of portions in a circumferential direction, and salient polesarranged between said permanent magnets, and wherein in a holdingportion holding said permanent magnets, a connection portion extendingin a radial direction along side walls of the permanent magnets has ashape of a narrow beam extending in a uniform thickness.
 12. Themotor-driven vehicle drive control apparatus according to claim 1,wherein a rotor of said motor is further provided with a plurality ofpermanent magnets arranged in a plurality of portions in acircumferential direction, and salient poles arranged between saidpermanent magnets, and wherein said salient poles are arrangeddownstream of a center between the permanent magnets in the rotationdirection of the motor.
 13. The motor-driven vehicle drive controlapparatus according to claim 7, wherein a rotor of said motor is furtherprovided with a plurality of permanent magnets arranged in a pluralityof portions in a circumferential direction, and salient poles arrangedbetween said permanent magnets, and wherein said salient poles arearranged downstream of a center between the permanent magnets in therotation direction of the motor.
 14. The motor-driven vehicle drivecontrol apparatus according to any one of claims 1 to 12, wherein saidmotor is directly connected to an output shaft of an engine.